Ion Pair Recognition Receptor Based on an Unsymmetrically 1,1′-Disubstituted Ferrocene–Triazole Derivative

The ferrocene–triazole derivative 4, available from 1,1′-bis­(diazido)­ferrocene by sequential functionalization through click-type chemistry and the Staudinger reaction, is elaborated as a lab-on-a-molecule for the selective sensing of HP2O73– and Hg2+. Receptor 4 behaves as a ratiometric fluorescent probe for HP2O73– with a good selectivity over other anions, whereas in the presence of Hg2+ it modifies the fluorescent emission of the pyrene unit, acting as a selective on–off fluorescent sensor for Hg2+ with a low detection limit. The most salient feature of compound 4 is its behavior as an excellent electrooptical ion pair recognition receptor able to simultaneously recognize Pb2+ cations in the presence of HP2O73– anion through multichannel perturbations of the redox potential of the ferrocene unit, the emission spectrum, and a noticeable color change from yellow to green.